Double pulse generator



Feb. 20, `1951 c, E CLEETON 2,541,986

DOUBLE PULSE GENERATOR Original Filed March l5, 1945 5 Sheets-Sheet 1 os "L ll. l O -NV- RECEIVER' l| l me/Mon CLAUD E. CLEETON 'a im DE 9/ Illa); d y j lu E AToRNEY Feb. 20, 1951 c. E. cLEr-:TON 2,541,986

Y DOUBLE PULSE GENERATOR Original Filed March 15, 1945 4 5 Sheets-Sheet 2 Imam/tm CLAUD E. CLEETON ATTQR N EY Feb. 20, 1951 c. E; cLEE'roN DOUBLE PULSE GENERATOR original Filed March `15, 1945 3 Sheets-Sheet 5 gmc/Mov CLAUD E. CLEETONv ATTORNEY atented Fei). 20, 1951 UNITED STATES PATENT -OFFICE 2,541,986 Y v l DOUBLE PULSE GENERATOR Claud E. Cleeton, Washington, D. C.' original application vMarch is, 1945,seria1 No.

582,966. Divided and this application September 26, 1947, Serial No. 776,394

v (c1. 25o-s) l(Granted under Vthe act of March 3, 1,883, as

4 Claims.

amended April 30, 1928; 370 0. G. 757') This invention relates to a method of transmission of radio frequency energy by means of a carrier envelope having definite characteristics, and is a division of -application S. N. 582,966, filed March 15, 1945.

An object of this invention is to vprovide a system by which intelligence transmitted in the form of pulses of radio frequency energy may be received. with a minimum of interference from man made or natural sources.

invention. The pulse generator I0 represents any suitable device, such as a free running multivibrator, which is designed to convey the intelligence of the transmissioneither by way of, for example, the number of pulses it produces over a given time interval or by way of the time occurrence of its pulses. The transmitter l2 is representative of any suitable pulse type made available by the prior art and is arranged to be Itis another object of this invention to provide a means vfor generating a signal of a denite shape or wave form foruse in controlling the operation of a radio pulse type transmitter.l

. Another object of this invention is to provide a means for converting the single pulse signals of a repetitive, non-repetitive or other type of pulse transmission system into a group of pulses wherein all lthe pulses in the group are of equal time duration and spacing.

Other objects and features of the present invention will become apparent uponl a careful consideration vof the following detailed description when taken together with the accompanying drawings.

Figure 1 is a schematic diagram, partly in block, showing one application of the present invention:

Figure 2 is a schematic diagram, partly in block,Y

showing the component parts of a receiving system which is to be used in this invention: and

, Figures 3 and 4 show a series of wave forms which are present at various points in the circuits of Figures 1 and 2 respectively and which are taken to illustrate the operation of these circuits. I

Specifically it is the purpose of the present in-v vention to provide a means for transforming each pulse signal of an otherwise conventional pulse transmission system into Va pair of pulse signals having equal time duration and spacing. The use of such a means permits the employment of a receiving system which is held singly responsive to the pulse transmission characteristics of the invention and unresponsive to other types of pulse signals, and therefore a receiving system which is less susceptible to interference caused by'either man-made or natural sources. Y

For purposes of illustration, the invention is shown in Figure 1 as incorporated in the transmitting equipment of an ordinary pulse transmission system. The pulse generator l0, pulse transmitter I2 and antenna I3 comprise theconventional components of the transmitting equipment while the apparatus indicated in general at I I comprises a preferred embodiment of the keyed either directly from the output of the circuit or indirectly through a modulator, if desired.

The circuit I, as here shown, is one specically designedto convert a single pulse output from the pulse generator I0 into a pair of equal time duration pulses, spaced in time by an amount equal to thetime duration of either of the pulses.

This circuit consists of a first switch tube 20, a

first ringing circuit 2|,.a clipping tube 22, a sec.- ond switch tube 24, a second ringing circuit 26, and three final limiting and shaping tubesY 2l, 28 and 3 I The rst ringing circuit 2| consists of a low Q anti-resonant circuit serially connected in the plate circuit of the switch tube 20. The latter is provided with a zero bias and is operated from the Youtput of the pulse generator I0. Pulse generator I0 produces the negative voltage pulses shown in wave form A of Figure 3, which are of suicient amplitude to drive tube 20 beyond cutoi. The plate current, which tube 20 normally draws, passes through the inductance of the ringing circuit 2| and thereby stores a certain amount of energy in this inductance. When a negative pulse is applied through condenser I9 to the control grid of the tube 20, the leading edge of this pulse tries to abruptly interrupt the normal plate current iioW through the inductance of the ringing circuit 2|. Due to the energy stored in the inductance, however, the current can not be stopped immediately so that the ringing circuit is thrown into oscillation as shown by the wave form B ofFigure 3. This oscillation occurs at thefresonant frequency of the ringing circuit and the first excursion thereof always starts at zero phase and rises positive to reach maximum amplitude on the rst half cycle. At the trailing Vedge of the negative voltage pulse, tube 20 isreturned to conduction and the ringing circuit is again set into' oscillation. This time, however, the oscillationsare of the opposite vphase and are highly damped by the conduction current of theV switch tube 20. A small resistance I3 (in the order of 5000 ohms) is connected across the ringing circuit 2| to increase the losses in the latter, andthereby to rapidly reduce the amplitude of all the oscillations occurring after the applied to the control grid on theclippingamplif-f.

er 22. The latter is so called-.becauseor tlie-.lfiigh=A negative bias applied to its control grid by Wayy of the potentiometer 23. -This potentiometer; is.

adjusted so that only the crest of the first positive half cycle of oscillationswill exceed-thev cut-- off bias, which is indicated by the-dotted-line-CO in Wave form B of Figure 3. Since the edges of the. oscillations` are. not. abrupt,. but are. more nearly. sine. waves,. the cut-oi line- COVv may be moved vertically. byl adjustment.. of. potentiometer 23.Lmtil. the time durationzof: the negative blocking pulse. produced at the;` plate of:` tube 22 is, as shown; by the vvavev form.C of Eigure13,.equal-. to about one-quarter of. thel natural period. ofthe secondringing. circuit 2S.- Thelatter. comprises a high. Q anti-resonant"l circuit serially. connectedinto the plate circuit: of. thesecondfswitchingtube 2 4.. This switch.. tube `likeswitch tube. 20 is operated at Zero bias, so that its normaliplate current` acts; to store a; certainv nite amountof energy in' the inductance. of: the .ringing circuit 2E. Then When. the negative blocking pulse.: output fromthe clipper amplifier. 22 which is of Vsufficient amplitude. to drive switch.. tube 2' below cut-olf, is applied to thecontrol grid of the latter, its leading abruptly in* rrupts thecurrentflow. through the inductance ofi the: second. ringing circuit.' to thereby; throw circuitl into oscillationasshownby the Wavefomr D oi. Figurek 3l and. inthe. same manner as the oscillations were startediinft-he first ringing circuit 2i.. These oscillations, like' those produced in the rstringing circuit, startiatizero. phase and rise positively at.: the. resonant. fre.- ouency of the' circuit; may` be, for example 50 kc. Then, atiaf point inatheoscillation Where. the rate of change ofi current is the greatest-g which. corresponds vto .the firstquarte'r cyclepoint,` the trailing edge" oi. ther negative pulse obtained from. the platewof tube-Z. restores conduction;r to

tubeT 2e; At; this instant:a1secondtrain ooscilla-l `tions is produced' in the. ringing circuit.'` 262. This trainis of sucha phase as torreinforce the initial oscillationsl vandv thus cause the amplitude of tliei second positive halfA cyclea of oscillations. to approach that ofthe iirst'. The oscillationsloccur'- ring after the second positive-half'cycle"arerap idly dampedby the conduction currentdrawn-by the switch tube The oscillatorsT` output `oi the second ringing circuit 2?VA is applied to the conirol gridfoi a; rst' clipping and shaping amplifier 27- Which'. containsa positive bias appli-edi to its: cathode', which' isV adjusted to permitonlyrthose positiveinputs over a certain amplitude, indicat'ed by the d'ottedcut"- oi line CGin Wave-form. D to be anripliecl;` shown in ferm Donlythev creststo the first twopositive halt-cycles ci* oscillation-:Will` exceed this cut-oli' bias. There is thusproduced at theL plate or tube 23.?? apair. of negative pulsesl'which'- Will have equal. time durations onlyfifthat portion of theiirst'two'positive-hal? cycles oi? oscillations fore to equalize the time duration and spacing of the pulses produced at the plate of tube 21 so that they resemble that shown by the wave form D, a condenser 25 is connected in shunt with tube 2l and. in combinatiorrwith. the plate resistance 29 forms a charging circuit.v Adjustments in the size of condenser 25 determines the slope of the trailing edges of the pulses appearing at the plate of tube 21 and therefore their base Width and spacing:

Thanegativedouble pulse output obtained from the plate oftube 21 is applied to the control grid ofi aa secondi. shaping. and limiting .amplifier 28. Thiscamplier'isoperated at zero bias and consequently willfVV amplify only that portion of the double-negative pulse input that does not exceed the cut-off bias. There is'thus produced at the plate ofV tube Z8 and applied to the control grid ortherlnal shaping amplier 3l the double positive pulse of wave form- F. This inal amplier 3L containsv a1 strong negative grid. bias set by potentiometer 3'2i and-.will consequently. amplify only the positive input above the. cut-orf lineV CO shownirrvfavev form?. After amplification and inversion by this tube the output pulses appear" as shown by the wave form G; These pulses arenoW of; suitable amplitude and. polarity to'cathode key for instance, the transmitter E2, thusv causing a double burst. of; radio. frequency.r energy to4 be radiated from antenna: I3;

receiver syst-ein. which isy held .solely responsive'. to pulsel signals .having transmission characteristicsof'. the foregoingv typeis shown infl'figurel 2. Thissyst'em-cornprises an'antenna I5, a' suitable pulseY type receiver |.i,.a discriminator indicated. inzgeneral. at. Il andV autilization network I. The latter, may bel an electrical'counter circuit=` a cathode.- ray tube for. visually monitoring` the received pulses orany: other suitabley device Iwhich may utilize the transmitted signals.

The dis'crirninatorv If'l is-v aY special circuitV designedsoaste-reconvert-a pair of pulse signals having the'- proper timeduration andgspacing into a single pulseoutput'and-isthe' subject of niyapplication entitled Pulse Discriminator- Circuiti S'. N. 5822097; l'edfMarch l0; 1.945. This'circuit compr-ises a` limiter: tube 34, aswitch tube 352 a; ringing circuit 3I'andA a iinai limiting tube'3`8'. In operation, the detectedoutputV ofthe-receiver E67, shovvnnby.` the'wave form Af of Figure l is in the form offan pair of negativepul'seswhich: area-pplied tothe controlgrid of the limiting amplier 342' This ampliiier, as shown, is operated at zero biassoas toont-off the bottoms of'the negative input pulses and apply to the control grid'off the switchit'ube' 35, a' pairouniform positivev voltage pulses. as-` showny bythe Wave form Bl ofv Figurev 42 SwitchV tube 35" isoperated withY a negative grid bias, applied; through resistance'vll', so that it Will amplify.l only'` lthose positive inputs that exceed thedotted'eut-offlin'e CG'shown in the wave form B: After amplication" and' inversion', they output or' theswitch-tube 35 appears: in the forni of a pair of.y negative rectangular voltage pulses. These pulses are as. sliovvn' in Wave' form' C in Figure .4 2 andv are. appliedV tov theringing circuitV 311i through the condenser 35. The latter ringing' circuitv is an anti-resonant circuit whichv is tunedf toV the resonant. frequency ofthe second ringing circuit 26 oftheltransmitt'er. At the leading edge'ofthe iirst'r pulse output' from the switchrtube 35' the voltage across the ringing' circuit" 3T is driven negati-'ve somewhat' as shown at Pin Wave formfD of? FigureI 4 to-tlier'ebyfshock the-ringing' 'circuiti clipped by tube 21T' haveequalibase'it'fi'mesV 'Il'ereiy 7&1 into oscillationat:v its" naturali frequency; Ai:

half cycle later when the shocked oscillations of the ringing circuit -have reached the iirst positive crest of oscillation the positive going trailing edge of the first pulse drives the oscillation of the ringing circuit still further positive as shown at O in wave form D. Thereafter the leading and trailing edges of the second pulse abruptly increase respectively the amplitude of the next succeeding negative and positive crests of oscillations as shown, and in such a manner that the shocked oscillations of the ringing circuit gradually build up to maximum amplitude and thereafter die away at a rate governed by the Q of the circuit. These oscillations are then applied to the control grid of the clipper amplifier 36. This amplifier contains a strong negative grid bias applied through potentiometer 33 so that it will only amplify the positive inputs that exceed its cut-off bias shown by the dotted line CO in wave form D.

Thus by a regulation of potentiometer 33 the cutg,

olf bias of tube 38 can be set so that not until after the ringing circuit 3l has received four successive kicks in the proper time order will the oscillations build up suliciently to overcome the cut-off bias of tube 3S. When the oscillations build up sul'liciently to o'vercome the cut-ofi" bias of tube 36 there will be produced at point 39 the wave form E. Pulses of either greater or less) time duration or of different spacing will not cause the oscillations to build up to the desired amplitude.

Since tubes 34 and 36 are operated as limiters the amplitude of the output signal at 39 will be substantially independent of the amplitude of the input signal and the output signal Will be substantially free from interference even where the general noise level is much higher than the signal level. This invention also lends itself to selective transmission simply by making use of a pulse group transmission having a greater number of pulses or pulses having different time duration and spacing.

For example, a three pulse system could be obtained simply by adjusting potentiometer 33 at the receiver so that the cut-off bias 'of the iinal limiting tube 38 is such that the ringing circuit 31 requires six successive voltage kicks in the proper time order before the amplitude of its oscilla` tion will build up sufliciently to exceed the cut-oil bias of tube 38. In this case, the rst ringing circuit 2| at the transmitter should be tuned to a frequency slightly below that of the second ringing circuit 26 and the bias of the first clipping tube 22 should be set by potentiometer 23 so that the time duration of the output pulse from the tube 22 will be such that the trailing edge of this ypulse will restore conduction to the second switch tube 24 at the crest of the secondpositive half cycle of oscillation instead of at the crest of the rst half cycle.

Although I have shown and described only a certain and specic embodiment of the invention it must be understood that I am fully aware of the many modications possible thereof.

The invention described herein may be manufactured and used by or for the Government of the United States of America for government which signal characteristics are represented by a series of rst impulses modulated to represent the intelligence to be transmitted, said rst impulses being spaced apart in time a large amount with respect to their duration, an arrangement for reducing the disturbing effects of interfering impulses comprising means for producing from each of said first impulses at least two indicating impulses spaced apart in time by a fixed time interval which is small with respect to the spacing of said first impulses, receiver means for receiving said indicating impulses, and discriminator means in said receiver means for discriminating between impulses spaced apart by said fixed time interval and all other impulses,v whereby only said spaced impulses may be used for signal indications. 1

Y2. A communication system according to claim l further comprising translator means for deriving the modulating signal from said received indicating impulses.

3. A receiver system for receiving pairs of impulses spaced apart a predetermined amount in time, each pair representing an increment of modulating signal energy in a modulated wave, means for receiving said pairs of impulses, discriminating means in said receiver for discriminating between pairs of impulses separated by said predetermined time delay and all other impulses, and translator means coupled to said discriminating means for reproducing the original modulating signal of said modulated wave.

4. A pulse transmission system comprising a first pulse generator means for generating a rst series of impulses modulated to represent the intelligence to be transmitted, said rst series of impulses being spaced apart in time a large amount with respect to their duration, and a second pulse generator coupled to said rst pulse generator means for producing from each im-Y pulse of said rst series of impulses at least two indicating impulses spaced apart in time by a fixed time interval which is independent of the duration of the rst'mpulses and small with respect to the spacing of the rst impulses.

CLAUD E. CLEETON.

REFERENCES' CITED The following references `are of record in the iile of this patent:

UNITED STATES PATENTS Number Name Date 2,145,332 Bedford Jan. 31, 1939 2,207,775 Bedford July 16, 1940y 2,223,812 Bedford Dec.A 3, 1940 2,266,401 Reeves Dec. 16, 1941 2,416,286 Busignies Feb. 25, 1947 2,416,304 Grieg Feb. 25, 1947 s, 2,433,407 Tahon Dec. 30, 1947 2,462,061 Beatty Feb. 22, 1949 2,464,667 Boosman et al Mar. 15, 1949 

